Piezoelectric materials are typically ABO3 perovskite-type metal oxides such as lead zirconate titanate (hereinafter referred to as PZT). PZT however contains lead in the A site of the perovskite structure thereof. This is an issue in terms of environment. Lead-free perovskite-type metal oxides are desired as piezoelectric materials.
Barium titanate has been known as a lead-free perovskite-type piezoelectric metal oxide. Also, in order to improve the characteristics of the lead-free perovskite-type piezoelectric material, barium titanate-based materials have been being developed.
In order to increase the piezoelectric constant of barium titanate at room temperature, PTL 1 discloses a barium titanate-based piezoelectric material in which Ca is substituted for part of the A site of barium titanate and Zr is substituted for part of the B site thereof. In order to increase the mechanical quality factor of barium titanate at room temperature, PTL 2 discloses a barium titanate-based piezoelectric material prepared by substituting Ca for part of the A site of barium titanate, and further adding Mn, Fe, or Cu to the Ca-substituted barium titanate.